Classifications

• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21C—NUCLEAR REACTORS
  • G21C1/00—Reactor types
  • G21C1/32—Integral reactors, i.e. reactors wherein parts functionally associated with the reactor but not essential to the reaction, e.g. heat exchangers, are disposed inside the enclosure with the core
• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21C—NUCLEAR REACTORS
  • G21C1/00—Reactor types
• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21C—NUCLEAR REACTORS
  • G21C1/00—Reactor types
  • G21C1/32—Integral reactors, i.e. reactors wherein parts functionally associated with the reactor but not essential to the reaction, e.g. heat exchangers, are disposed inside the enclosure with the core
  • G21C1/322—Integral reactors, i.e. reactors wherein parts functionally associated with the reactor but not essential to the reaction, e.g. heat exchangers, are disposed inside the enclosure with the core wherein the heat exchanger is disposed above the core
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E30/00—Energy generation of nuclear origin
  • Y02E30/30—Nuclear fission reactors

Definitions

• the invention relates to a pressurized water nuclear reactor of integrated and compact design.
• the invention applies in particular to nuclear reactors of small and medium powers, that is to say in particular to reactors whose power is less than or equal to about 600 M e.
• Existing pressurized water nuclear reactors usually include a vessel containing the core of the reactor, primary circuits connecting the vessel to steam generators placed outside thereof and primary pumps capable of circulating water under pressure in each of the primary circuits, to transfer the heat produced by the nuclear reaction to the reactor core to the steam generators.
• a pressurizer also placed outside the tank ensures the pressurization of the water contained in the tank and in the primary circuits.
• Reactors of the integrated type differ from the preceding ones in that the steam generators are placed inside the reactor vessel, in an annular region delimited between the peripheral wall of the vessel and a partition inside it.
• the primary pumps remain, however, outside the tank, to which they are connected by suitable pipes.
• the control rod control mechanisms are also located outside the tank, as in traditional reactors.
• a sealed enclosure provides overall containment of the primary circuit.
• a single steam generator forms the cover of the vessel.
• a first drawback concerns their design.
• the primary pumps and the pressurizer are located outside the tank.
• the control rods are driven by motors located outside the tank and the mechanism contains a bevel gear.
• the complexity of these devices does not allow the design of high power cores (greater than 500 or 1000 MW thermal) due to the space required due to the need for numerous control bars.
• a second drawback is their investment cost, due in particular to the architecture of the buildings imposed by the design recalled above.
• Another drawback concerns the existence of a certain number of accident situations also inherent in the design of existing reactors. These situations require the presence of numerous systems for saving and discharging residual power which significantly increase the cost of these reactors.
• the object of the invention is to at least partially solve the problems posed by existing pressurized water nuclear reactors.
• the object of the invention is in particular to propose a compact pressurized water nuclear reactor whose original design allows it to be more economical in construction and inherently safer than existing reactors, while possibly allowing the use of different types of nuclear fuel assemblies.
• this objective is achieved at least partially thanks to a compact pressurized water nuclear reactor, comprising a vessel closed by a cover, a reactor core housed in the vessel, a steam generator forming the cover of the tank, primary pumping means capable of circulating water between the reactor core and the steam generator, and a pressurizer capable of ensuring the pressurization of the water, characterized in that the pumping means and the pressurizer are housed in the reactor vessel, so as to form a primary circuit fully integrated in said vessel.
• the fully integrated reactor design according to the invention makes it possible to reduce investment costs, in particular by simplifying the architecture of the buildings.
• This integrated design also eliminates a number of accident situations that are difficult to manage from a safety point of view and impose costly management systems.
• mechanisms for controlling the control rods are also integrated in the reactor vessel.
• a substantially annular partition projects downwards from the cover and delimits, inside the tank, a peripheral region and a central region.
• the reactor core and the pressurizer are then housed respectively at the bottom and at the top of the central region and the pumping means are housed at the top of the peripheral region.
• the pressurizer comprises an annular tank, with inverted U-shaped section, open at the bottom and the top of which communicates with a balloon forming a source of steam, means being provided for supplying said balloon with water taken from the peripheral region, below the pumping means.
• a venturi system supplied with water contained in the central region, is placed in the peripheral region to create in it a natural circulation of water, from top to bottom, in the event of failure of the means. pumping.
• an emergency cooling exchanger is advantageously placed in the peripheral region, below the venturi system.
• the reactivity of the reactor core is controlled in the absence of neutron poison soluble in cooling water.
• the compact pressurized water nuclear reactor comprises a vessel 10, of vertical axis.
• the upper end of the tank 10 has an opening normally closed by a steam generator 12 thus forming the cover of the tank.
• the enclosed volume contained inside the tank 10, below the cover materialized by the steam generator 12, is delimited internally by a substantially annular partition 15, which projects downward from said cover.
• the partition 15, centered on the vertical axis of the tank 10, thus separates this closed volume into a central region 16 and a peripheral region 18, which communicate with each other at the bottom of the tank 10.
• the reactor core 14 is housed at the bottom of the central region 16. It is formed of nuclear fuel assemblies arranged in bundles in a vertical direction. These assemblies can be of conventional design or of a different type. In the latter case, it may especially be assemblies of more recent design such as advanced assemblies, for example consumers of actinides.
• the core 14 of the reactor can in particular be formed from 157 assemblies of 17 ⁇ 17 rods, as in water reactors under pressure of 900 MWe existing. However, the specific power is reduced by 25% compared to these reactors.
• the steam generator 12 comprises a horizontal base plate 20 forming the actual tank cover and an external envelope 22 sealingly connected to the peripheral edge of the base plate 20 and delimiting therewith a closed secondary space 24.
• the steam generator 12 also comprises a bundle of inverted U-shaped tubes 26, placed in the closed secondary space 24. More precisely, the two ends of each of the tubes 26 are fixed on the base plate 20 so that one of these ends opens into the central region 16 and the other end opens into the peripheral region 18.
• the enclosed volume delimited inside the tank 10 as well as inside the tubes 26 forms the primary circuit of the reactor.
• This completely integrated primary circuit is filled with pressurized water.
• the circulation of water in the primary circuit of the reactor is ensured by primary pumping means, materialized by a number primary pumps 28 housed directly in the upper part of the peripheral region 18.
• the primary pumps 28 circulate the water in the direction of the arrows in Figure 1.
• the pumps 28 circulate the water down the tank 10 in the region peripheral 18, then upwards through the heart 14 in the central region 16 and finally from bottom to top, then from top to bottom in the tubes 26 of the steam generator 12.
• the primary pumps 28 can take different forms. Among the pumps that can be used, mention will in particular be made of radial pumps, pump-injectors and axial turbopumps. Radial pumps are flooded rotor pumps which are arranged at the top of the tank and oriented in a radial direction relative to the vertical axis thereof. This type of pump is described in reference [1].
• the upper part of the peripheral region 18 comprises a series of injectors or jet pumps. The injector is supplied with a low flow rate but at high pressure to circulate most of the coolant without leaving the tank. The high pressure supply flow to the injector comes from a pump located outside the tank.
• vertical turbopumps can also be placed at the top of the peripheral region 18.
• the turbine is then supplied with high pressure primary water from a pump located outside the tank.
• the axial turbopump fulfills the same "hydraulic transformer" function as the injector in the previous case, but with a rotating part.
• the turbine can be replaced by an electric motor whose windings are covered with a sealing skin to isolate them from the heat transfer fluid.
• the pressurizer 30 is also integrated in the tank 10 of the reactor. More specifically, the pressurizer 30 is in the form of an annular tank housed at the top of the central region 16 of the tank 10, immediately below the base plate 20. This tank is delimited by a wall which presents in section the shape of an inverted U. The tank forming the pressurizer 30 is open downwards so as to open directly into the central region 16 of the tank 10.
• the upper part of the tank forming the pressurizer 30 is filled with steam.
• the top of said tank is supplied with a two-phase water-steam mixture through a pipe 34 connected to a balloon 32 of small volume placed outside the tank 10 and acting as a source of steam.
• the balloon 32 is equipped with heating rods 36.
• the water supply to the balloon 32 is provided by another pipe 38, which connects said balloon to the peripheral region 18 of the tank 10, just downstream of the primary pumps 28.
• control bars 40 used to control the reactivity in the heart 14 of the reactor.
• control rods 40 and their control mechanisms are also integrated in the reactor vessel. This arrangement is dictated by the impossibility of using standard mechanisms (electromagnetic mechanisms placed outside the tank) due to the presence of the steam generator above the tank 10.
• control rod 40 for one or two nuclear fuel assemblies and leads to suppress local power excursions due to an ejection of a control rod, like this may be feared in the standard design pressurized water reactor.
• This allows the control rods 40 to ensure alone the control of the reactivity in the core, which authorizes an absence of neutron poison soluble in the cooling water of the core 14 of the reactor.
• cooling water from the reactor core 14 is also made possible by the fact that the low power density makes it possible to accommodate local power peaks slightly stronger than in pressurized water reactors of standard design.
• the low power density and the drop in the operating point compared to these standard reactors reduce the need for reactivity control and also help to authorize the removal of soluble boron.
• control rods with control mechanisms integrated in the vessel 10 of the reactor can be constituted either by a system of bars controlled by a hydraulic device, or by a system of fluid bars, or even by these two systems combined so as to ensure a redundancy.
• Control rods controlled by a hydraulic device are described in particular in reference [2].
• Such a mechanism consists of a hollow piston and a movable cylinder.
• the piston is fixed on the support plate of the heart and the cylinder is grooved in the lower part.
• the geometries of the piston and cylinder grooves are identical. Maintaining the position of the cylinder is obtained by admitting a given flow rate of primary fluid inside the piston. This causes the cylinder to rise or fall, by a height equal to the pitch of the grooves, by temporarily increasing or reducing this flow rate of primary fluid.
• a system of fluid bars is described in document FR-A-2 765 722. In this system, a liquid salt containing neutron absorbents is displaced in the heart through a bundle of guide tubes.
• the movement of these absorbents is carried out by means of a gas acting as a piston and acting on the salt.
• the absorbent salt reserve is arranged above the assemblies.
• An automatic stop of the power of the heart can be carried out by a rapid introduction of the absorbents.
• the axial and radial distributions of the absorbent salt can be controlled to flatten the shape of the flow in the heart.
• the operating point of the compact reactor according to the invention is advantageously chosen at a relatively low pressure and temperature. Thus, a pressure of around 80 to 90 bar in the primary circuit is retained.
• the pressure in the secondary circuit is approximately 30 bar, which leads to a net efficiency of 30%.
• the thermal power of the core is 2000 MW.
• the compact reactor according to the invention is of preferably equipped with backup or security systems.
• These backup systems include means for evacuating residual power, safety injection means and means for controlling the primary pressure.
• the means for discharging the residual power are placed on the one hand on the primary circuit and on the other hand on the secondary circuit of the reactor. This arrangement makes it possible to ensure a diversity of means as a function of the abnormal transient, taking into account the fact that the reactor comprises a single steam generator.
• the power evacuation system installed on the primary circuit comprises heat exchangers 42 placed in the peripheral region 18 of the tank. These exchangers are connected to an emergency cooling circuit (not shown) outside the vessel 10 of the reactor.
• the system located on the primary circuit also includes a venturi system 44 placed in the peripheral region 18, above the exchangers 42.
• the venturi system 44 is formed between the partition 15 and a ferrule 46 connected to the peripheral wall of the tank 10.
• the shape of the shell 46 is such that the flow section decreases progressively going downwards inside the peripheral region 18, until a constriction formed at the base of the venturi system 44. Au level of this constriction, the venturi system is supplied with water coming from the central region 16 through openings 48 provided for this purpose in the partition 15.
• the venturi is dimensioned so that in normal operation, the pressure at 44 is substantially equal to the pressure at 48. In this way, the short circuit flow between region 16 and region 18 can be minimized. In the case of pumps stopped, the openings 48 allow natural convection between the heart 14 and the exchangers 42 to evacuate the power released in the heart.
• the residual power evacuation system located on the secondary circuit can in particular comprise a secondary condensation system associated with a thermal valve, or a system with steam injector.
• the secondary condensation system can in particular be of the type described in reference [3] and the thermal valve can be of the type described in document FR-A-2 725 508.
• a steam injector system can be produced as described in reference [4].
• Safety injection means are also provided, in order to ensure the presence of a sufficient volume of water in the primary circuit, in the event of an accident.
• a low flow system is sufficient.
• the discharge pressure of the safety injection system can be, for example, around 25 bar.
• the confinement of the compact reactor which has just been described may in particular comprise a pressure suppression enclosure 47 containing the primary circuit.
• This enclosure can then be limited to the volume of the compartment located under the horizontal plane of junction of the tank 10 and the steam generator 12.
• the steam generator is then placed in a swimming pool 48 located above this plane, used for the core reloading and maintenance operations.

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• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Plasma & Fusion (AREA)
• General Engineering & Computer Science (AREA)
• High Energy & Nuclear Physics (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Structure Of Emergency Protection For Nuclear Reactors (AREA)
• Monitoring And Testing Of Nuclear Reactors (AREA)
• Jet Pumps And Other Pumps (AREA)
• Structures Of Non-Positive Displacement Pumps (AREA)

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• 2001
  • 2001-11-26 FR FR0115266A patent/FR2832846B1/fr not_active Expired - Lifetime
• 2002
  • 2002-11-25 JP JP2003548258A patent/JP4313204B2/ja not_active Expired - Fee Related
  • 2002-11-25 CN CNB02823278XA patent/CN1282198C/zh not_active Expired - Fee Related
  • 2002-11-25 US US10/495,526 patent/US7154982B2/en not_active Expired - Lifetime
  • 2002-11-25 ES ES02795392T patent/ES2339344T3/es not_active Expired - Lifetime
  • 2002-11-25 KR KR1020047007870A patent/KR100972344B1/ko active IP Right Grant
  • 2002-11-25 WO PCT/FR2002/004030 patent/WO2003046927A2/fr active Application Filing
  • 2002-11-25 AU AU2002360186A patent/AU2002360186A1/en not_active Abandoned
  • 2002-11-25 DE DE60235043T patent/DE60235043D1/de not_active Expired - Lifetime
  • 2002-11-25 EP EP02795392A patent/EP1464058B1/de not_active Expired - Lifetime

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